What is the primary function of a septic tank?

The primary function of a septic tank is to treat and store sewage. A septic tank is part of a decentralized wastewater treatment system which is designed to collect and break down household wastewater. When sewage enters the tank, solids are allowed to settle at the bottom, forming sludge, while lighter materials such as oils and grease float to the top, creating scum. The tank's design facilitates anaerobic digestion, where bacteria break down organic matter, reducing the volume of solids.

This biological process helps to partially treat the sewage before the effluent is discharged into a drain field, where it undergoes further treatment as it percolates through the soil. This process helps to minimize pollution and protect groundwater. While other options may involve various water management functions, they do not align with the specific purpose of a septic tank, which is focused on managing sewage treatment and storage.